A former Port Authority maintenance supervisor at La Guardia airport is suing the agency, claiming that he was targeted for harassment and then canned after reporting thievery by his co-workers.

James D’Amico claims he was fired after 25 years with the bi-state agency in retaliation for reporting rampant misconduct to the Port Authority’s inspector general’s office.

In papers filed in Brooklyn federal court, D’Amico says he witnessed agency employees at La Guardia steal granite tiles intended for airport terminals but that were instead installed in the workers’ private residences.

He also charged that workers devised schemes to increase their overtime pay, such as delaying runway repairs so that they needed to be performed on weekends or prolonging airport snow alerts so they could work extra shifts — a practice referred to as “gravy overtime.”

The suit also charges that agency supervisors at La Guardia paid kickback to firms awarded snow removal contracts, while contractors doled out favors — such as plowing snow at airport workers’ homes.

D’Amico also charges that after the death of a PA worker at the airport, a colleague open the deceased man’s locker, discovered $30,000 in cash and stole $10,000.

The suit does not explain why so much money was being kept in the work locker.

After workers learned that he had spoken with internal agency investigators about the fraud and theft problems at the airport, D’Amico says he was targeted for abuse and called a “rat.”

D’Amico says he later developed health problems on the job and eventually was terminated.

He’s seeking unspecified damages from the agency, charging that he was a victim of discrimination because he was disabled with his illness.